Induction of lipogenesis in white fat during cold exposure in mice: link to lean phenotype.

This corrects the article DOI: 10.1038/ijo.2016.228.

Induction of lipogenesis in white fat during cold exposure in mice: link to lean phenotype.

BACKGROUND/OBJECTIVE: Futile substrate cycling based on lipolytic release of fatty acids (FA) from intracellular triacylglycerols (TAG) and their re-esterification (TAG/FA cycling), as well as de novo FA synthesis (de novo lipogenesis (DNL)), represent the core energy-consuming biochemical activities of white adipose tissue (WAT). We aimed to characterize their roles in cold-induced thermogenesis and energy homeostasis. METHODS: Male obesity-resistant A/J and obesity-prone C57BL/6J mice maintained at 30 °C were exposed to 6 °C for 2 or 7 days. In epididymal WAT (eWAT), TAG synthesis and DNL were determined using in vivo 2H incorporation from 2H2O into tissue TAG and nuclear magnetic resonance spectroscopy. Quantitative real-time-PCR and/or immunohistochemistry and western blotting were used to determine the expression of selected genes and proteins in WAT and liver. RESULTS: The mass of WAT depots declined during cold exposure (CE). Plasma levels of TAG and non-esterified FA were decreased by day 2 but tended to normalize by day 7 of CE. TAG synthesis (reflecting TAG/FA cycle activity) gradually increased during CE. DNL decreased by day 2 of CE but increased several fold over the control values by day 7. Expression of genes involved in lipolysis, glyceroneogenesis, FA re-esterification, FA oxidation and mitochondrial biogenesis in eWAT was induced during CE. All these changes were more pronounced in obesity-resistant A/J than in B6 mice and occurred in the absence of uncoupling protein 1 in eWAT. Expression of markers of glyceroneogenesis in eWAT correlated negatively with hepatic FA synthesis by day 7 in both strains. Leptin and fibroblast growth factor 21 plasma levels were differentially affected by CE in the two mouse strains. CONCLUSIONS: Our results indicate integrated involvement of (i) TAG/FA cycling and DNL in WAT, and (ii) hepatic very-low-density lipoprotein-TAG synthesis in the control of blood lipid levels and provision of FA fuels for thermogenesis in cold. They suggest that lipogenesis in WAT contributes to a lean phenotype.

A mechanistic approach to modelling the formation of a drug reservoir in the skin.

It has been shown that prolonged systemic presence of a drug can cause a build-up of that drug in the skin. This drug 'reservoir', if properly understood, could provide useful information about recent drug-taking history of the patient. We create a pair of coupled mathematical models which combine to explore the potential for a drug reservoir to establish based on the kinetic properties of the drug. The first compartmental model is used to characterise time-dependent drug concentrations in plasma and tissue following a customisable drug regimen. Outputs from this model provide boundary conditions for the second, spatio-temporal model of drug build-up in the skin. We focus on drugs that are highly bound as this will restrict their potential to move freely into the skin but which are lipophilic so that, in the unbound form, they would demonstrate an affinity to the outer layers of the skin. Buprenorphine, a drug used to treat opiate addiction, is one example of a drug satisfying these properties. In the discussion we highlight how our study might be used to inform future experimental design and data collection to provide relevant parameter estimates for reservoir formation and its potential to contribute to enhanced drug monitoring techniques.

Influence of pulmonary factors on pulse oximeter saturation in preterm infants.

AIM: To describe how the stability of oxygen saturation measured by pulse oximetry (SpO2%) varies within and between infants with bronchopulmonary dysplasia (BPD). METHODS: Clinically stable infants with BPD had SpO2 measured at different inspired oxygen concentrations (FIO2 expressed as %). A computer model of gas exchange, that is, ventilation/perfusion ratio (VA/Q) and shunt, plotted the curve of SpO2 versus FIO2 best fitting these data. The slope of this curve is the change in SpO2 per % change in FIO2, hence SpO2 stability, calculated at each SpO2 from 85% to 95%. RESULTS: Data from 16 infants with BPD previously described were analysed. The dominant gas exchange impairment was low VA/Q (median 0.35, IQR, 0.16-0.4, normal 0.86). Median shunt was 1% (IQR, 0-10.5; normal <2%). Slope varied markedly between infants, but above 95% SpO2 was always <1.5. In infants with least severe BPD (VA/Q ≈0.4, shunt ≤2%) median slope at 85% SpO2 was 5.1 (IQR, 3.7-5.5). With more severe BPD (VA/Q ≤0.3) slope was flatter throughout the SpO2 range. The highest FIO2 for 90% SpO2 was in infants with the lowest VA/Q values. CONCLUSIONS: In infants with BPD, there was large variation in the slope of the curve relating SpO2% to inspired oxygen fraction in the SpO2 range 85%-95%. Slopes were considerably steeper at lower than higher SpO2, especially in infants with least severe BPD, meaning that higher SpO2 target values are intrinsically much more stable. Steep slopes below 90% SpO2 may explain why some infants appear dependent on remarkably low oxygen flows.

Validation of an Arabic version of the Oswestry index in Saudi Arabia.

OBJECTIVE: The aim of this study was to adapt and validate the Tunisian version of the Oswestry Disability Index (ODI) within a Saudi Arabian population. METHOD: The translation of items 8 and 10 taken out of the Tunisian version was conducted according to Beaton's method. Adaptations were made after a pilot study on 100 patients. The validation study included 100 patients suffering from chronic low back pain aged 18 to 65 years old. Intra-observer reliability was assessed using the intra-class coefficient (ICC). Spearman rank correlation coefficient, the Kruskall-Wallis test and factor analysis were used to evaluate construct validity (convergent and divergent validity). Internal consistency was assessed by Cronbach's alpha coefficient. RESULTS: One hundred Saudi patients were included in the study. Intra-observer reliability was excellent (ICC: 0.99). The correlations of the index with the VAS pain scale (r=0.708), the Roland-Morris Low Back Pain Disability (r=0.656), and the Quebec Back Pain Disability Scale (r=0.792) suggest good construct validity. Factor analysis unveiled two main factors explaining a cumulative percentage variance of 63.5%. The first factor represents static activities and the second factor represents dynamic activities. CONCLUSION: The Arabic version of the ODI adapted to the Saudi population has high metrological qualities. Further studies assessing its responsiveness to change should be conducted.

Diffusion tensor imaging correlates with the clinical assessment of disease severity in cervical spondylotic myelopathy and predicts outcome following surgery.

BACKGROUND AND PURPOSE: CSM is a common neurologic disease that results in progressive disability and eventual paralysis without appropriate treatment. Imaging plays a significant role in the evaluation of CSM and has evolved with recent technical advances. We sought to systematically explore the relationship between clinical disease severity and DTI in CSM, and to investigate the potential use of DTI in surgical decision-making models. MATERIALS AND METHODS: MR imaging studies and clinical assessments were prospectively collected on 30 patients with CSM. Spearman correlations were used to investigate associations between clinical disease severity and FA at the time of diagnosis. Clinical assessment was performed using mJOA, Nurick, Short Form-36, and NDI scores. Fifteen patients with CSM subsequently underwent decompressive surgery; Spearman correlation and logistic regression were applied to this cohort to study the relationship between baseline DTI measurements and postoperative outcome. Conventional imaging (spinal cord T2 signal intensity and degree of stenosis) was evaluated for comparison with DTI. RESULTS: At diagnosis, FA demonstrated a strong correlation with baseline mJOA (r = 0.62, P < .01) and Nurick (r = -0.46, P = .01) scores. After surgery, recovery of function demonstrated by improvement in NDI score was associated with higher FA values on preoperative DTI (r = -0.61, P = .04). Severely affected patients with CSM with disproportionately high FA tended to achieve greater mJOA scores after surgery compared with subjects with lower FA (P = .08). T2 signal intensity was associated with functional status at baseline but did not predict postoperative outcome; degree of stenosis lacked any significant correlation with clinical parameters. CONCLUSIONS: DTI may be a useful diagnostic tool for assessing disease severity in CSM. The predictive value of DTI regarding postoperative outcome may improve surgical decision-making and facilitate health care outcomes research.

Impaired insulin stimulation of muscular ATP production in patients with type 1 diabetes.

OBJECTIVE: in type 2 diabetic patients and their first-degree relatives, insulin resistance (IR) is associated with impairment of insulin-stimulated myocellular glucose-6-phosphate (g6p) and unidirectional flux through ATP synthase (fATP), suggesting the presence of inherited abnormal mitochondrial oxidative fitness. We hypothesized that patients with long-standing type 1 diabetes may also exhibit insulin resistance as well as lower fATP. DESIGN: this single-centre trial was registered at ClinicalTrials.gov (NCT00481598). SUBJECTS: we included eight nonobese type 1 diabetic patients (mean diabetes duration: 17 years) with near-target glycaemic control [haemoglobin A1c (HbA1c): 6.8 ± 0.4%] during treatment with continuous subcutaneous insulin infusion pumps and eight healthy volunteers (HbA1c: 5.4 ± 0.2%) of comparable age, body mass and level of physical activity. OUTCOME MEASURES: myocellular fATP, g6p and intramyocellular lipid content (IMCL) were measured with (1) H/(31) P magnetic resonance spectroscopy during fasting and hyperinsulinaemic-euglycaemic clamp tests. RESULTS: fasting fATP, g6p and IMCL did not differ between groups. During stimulation by insulin, type 1 diabetic patients exhibited approximately 50% (P < 0.001) lower whole-body glucose disposal along with approximately 42% (P = 0.003) lower intramyocellular g6p and approximately25% (P = 0.024) lower fATP. Insulin-stimulated fATP correlated positively with whole-body insulin sensitivity (R = 0.706, P = 0.002) and negatively with HbA1c (R = -0.675, P = 0.004). CONCLUSIONS: despite documented near-target glycaemic control for 1 year, nonobese patients with long-standing type 1 diabetes can exhibit insulin resistance. This associates with lower insulin-stimulated flux through muscular ATP synthase which could result from glucose toxicity.

A simplified method for deriving shunt and reduced VA/Q in infants.

BACKGROUND: Right to left shunt and regional hypoventilation (reduced ventilation/perfusion ratio (V(A)/Q)) have different effects on the curve relating inspired oxygen (P(I)O(2)) to oxygen saturation measured by pulse oximetry (SpO(2)) and can be derived non-invasively from measurements of SpO(2) and inspired oxygen pressure (P(I)O(2)) using complex models of gas exchange. We developed a simpler computerised "slide-rule" method of making these derivations. AIMS: To describe the slide-rule method and determine agreement between measurements derived with this and a more complex algorithm. METHODS: Series of P(I)O(2) versus SpO(2) data points obtained during 43 studies in 16 preterm infants with bronchopulmonary dysplasia were analysed. Percentage shunt and the degree of right shift (kPa) of the P(I)O(2) versus SpO(2) curve compared with the oxyhaemoglobin dissociation curve (a measure of V(A)/Q) were determined for each dataset with both methods, and the results were compared using the method of Bland and Altman. RESULTS: The computer slide-rule method produced results for all 43 datasets. The more complex model could derive results for 40/43 datasets. The mean differences (95% limits of agreement) between the two methods for measurements of shunt were -1.7% (-6.5 to +3.5%) and for measurements of right shift were 0.3 kPa (-2.9 to +3.6 kPa). CONCLUSION: The slide-rule method was reliable for deriving shunt and right shift (reduced V(A)/Q) of the P(I)O(2) versus SpO(2) curve when compared with the more complex algorithm. The new method should enable wider clinical application of these measurements of oxygen exchange.

Sources of hepatic triglyceride accumulation during high-fat feeding in the healthy rat.

Hepatic triglyceride (HTG) accumulation from peripheral dietary sources and from endogenous de novo lipogenesis (DNL) was quantified in adult Sprague-Dawley rats by combining in vivo localized (1)H MRS measurement of total hepatic lipid with a novel ex vivo (2)H NMR analysis of HTG (2)H enrichment from (2)H-enriched body water. The methodology for DNL determination needs further validation against standard methodologies. To examine the effect of a high-fat diet on HTG concentrations and sources, animals (n = 5) were given high-fat chow for 35 days. HTG accumulation, measured by in vivo (1)H MRS, increased significantly after 1 week (3.85 +/- 0.60% vs 2.13 +/- 0.34% for animals fed on a standard chow diet, P < 0.05) and was maintained until week 5 (3.30 +/- 0.60% vs 1.12 +/- 0.30%, P < 0.05). Animals fed on a high-fat diet were glucose intolerant (13.3 +/- 1.3 vs 9.4 +/- 0.8 mM in animals fed on a standard chow diet, for 60 min glycemia after glucose challenge, P < 0.05). In control animals, DNL accounted for 10.9 +/- 1.0% of HTG, whereas in animals given the high-fat diet, the DNL contribution was significantly reduced to 1.0 +/- 0.2% (P < 0.01 relative to controls). In a separate study to determine the response of HTG to weaning from a high-fat diet, animals with raised HTG (3.33 +/- 0.51%) after 7 days of a high-fat diet reverted to basal HTG concentrations (0.76 +/- 0.06%) after an additional 7 days of weaning on a standard chow diet. These studies show that, in healthy rats, HTG concentrations are acutely influenced by dietary lipid concentrations. Although the DNL contribution to HTG content is suppressed by a high-fat diet in adult Sprague-Dawley rats, this effect is insufficient to prevent overall increases in HTG concentrations.

Sources of hepatic glucose production by 2H2O ingestion and Bayesian analysis of 2H glucuronide enrichment.

The contribution of gluconeogenesis to hepatic glucose production (GP) was quantified after (2)H(2)O ingestion by Bayesian analysis of the position 2 and 5 (2)H-NMR signals (H2 and H5) of monoacetone glucose (MAG) derived from urinary acetaminophen glucuronide. Six controls and 10 kidney transplant (KTx) patients with cyclosporine A (CsA) immunosuppressant therapy were studied. Seven KTx patients were lean and euglycemic (BMI = 24.3 +/- 1.0 kg/m(2); fasting glucose = 4.7 +/- 0.1 mM) while three were obese and hyperglycemic (BMI = 30.5 +/- 0.7 kg/m(2); fasting glucose = 7.1 +/- 0.5 mM). For the 16 spectra analyzed, the mean coefficient of variation for the gluconeogenesis contribution was 10% +/- 5%. This uncertainty was associated with a mean signal-to-noise ratio (SNR) of 79:1 and 45:1 for the MAG H2 and H5 signals, respectively. For control subjects, gluconeogenesis contributed 54% +/- 7% of GP as determined by the mean and standard deviation (SD) of individual Bayesian analyses. For the lean/normoglycemic KTx subjects, the gluconeogenic contribution to GP was 62% +/- 7% (P = 0.06 vs. controls), while hyperglycemic/obese KTx patients had a gluconeogenic contribution of 68% +/- 3% (P < 0.005 vs. controls). These data suggest that in KTx patients, an increased gluconeogenic contribution to GP is strongly associated with obesity and hyperglycemia.

Late Pleistocene and Holocene environmental history of the Iguala Valley, Central Balsas Watershed of Mexico.

The origin of agriculture was a signal development in human affairs and as such has occupied the attention of scholars from the natural and social sciences for well over a century. Historical studies of climate and vegetation are closely associated with crop plant evolution because they can reveal the ecological contexts of plant domestication together with the antiquity and effects of agricultural practices on the environment. In this article, we present paleoecological evidence from three lakes and a swamp located in the Central Balsas watershed of tropical southwestern Mexico that date from 14,000 B.P. to the modern era. [Dates expressed in B.P. years are radiocarbon ages. Calibrated (calendar) ages, expressed as cal B.P., are provided for dates in the text.] Previous molecular studies suggest that maize (Zea mays L.) and other important crops such as squashes (Cucurbita spp.) were domesticated in the region. Our combined pollen, phytolith, charcoal, and sedimentary studies indicate that during the late glacial period (14,000-10,000 B.P.), lake beds were dry, the climate was cooler and drier, and open vegetational communities were more widespread than after the Pleistocene ended. Zea was a continuous part of the vegetation since at least the terminal Pleistocene. During the Holocene, lakes became important foci of human activity, and cultural interference with a species-diverse tropical forest is indicated. Maize and squash were grown at lake edges starting between 10,000 and 5,000 B.P., most likely sometime during the first half of that period. Significant episodes of climatic drying evidenced between 1,800 B.P. and 900 B.P. appear to be coeval with those documented in the Classic Maya region and elsewhere, showing widespread instability in the late Holocene climate.

Sources of endogenous glucose production in the Goto-Kakizaki diabetic rat.

Plasma glucose, insulin and glucose tolerance were quantified in diabetic Goto-Kakizaki (GK) rats (342+/-45 g, n = 5) and compared with weight-matched non-diabetic Wistars (307+/-30 g, n = 8). Compared to Wistars, GK rats had higher fasting plasma insulin (219+/-50 versus 44+/-14 pmol/l, P<0.002) and glucose (9.2+/-2.3 versus 5.5+/-0.5 mmol/l, P<0.025). GK rats showed impaired glucose tolerance (IPGTT 2 h plasma glucose=14+/-1.5 versus 6.4+/-0.1 mmol/l, P<0.001). Endogenous glucose production (EGP) from glycogenolysis, phosphoenolpyruvate (PEP) and glycerol after 6 hours of fasting was quantified by a primed infusion of [U-(13)C]glucose and (2)H(2)O tracers and (2)H/(13)C NMR analysis of plasma glucose. EGP was higher in GK compared to Wistar rats (191+/-16 versus 104+/-27 mumol/kg per min, P<0.005). This was sustained by increased gluconeogenesis from PEP (85+/-12 versus 35+/-4 mumol/kg per min, P<0.02). Gluconeogenesis from glycerol was not different (20+/-3 in Wistar versus 30+/-6 mumol/kg per min for GK), and glycogenolysis fluxes were also not significantly different (76+/-23 mumol/kg per min for GK versus 52+/-19 mumol/kg per min for Wistar). The Cori cycle accounted for most of PEP gluconeogenesis in both Wistar and GK rats (85+/-15% and 77+/-10%, respectively). Therefore, increased gluconeogenesis in GK rats is largely sustained by increased Cori cycling while the maintenance of glycogenolysis indicates a failure in hepatic autoregulation of EGP.

Use of polymerase chain reaction as a diagnostic tool for neonatal sepsis can result in a decrease in use of antibiotics and total neonatal intensive care unit length of stay.

OBJECTIVE: To retrospectively determine if a negative 16S ribosomal RNA (rRNA) polymerase chain reaction (PCR) (PCR(-)) could lead to a decrease in the number of antibiotic doses and neonatal intensive care unit (NICU) length of stay (LOS) for infants admitted to the NICU for presumed early-onset sepsis (EOS) with negative blood culture results (BC(-)). STUDY DESIGN: Analysis included 419 infants, greater than 35 weeks gestational age, with PCR(-), BC(-) and LOS > 48 h. Both the investigators and clinical care team were unaware of the PCR results. The actual number of antibiotic doses (AAD) administered was compared to an estimated number of antibiotics doses (EAD) that would have been given until PCR(-) results were available by 18 h. The number of antibiotic doses saved was calculated as (AAD-EAD). The actual NICU LOS in hours (aLOS) for a subset of infants who remained in the hospital primarily for antibiotic therapy was compared to an estimated LOS (eLOS) if infants with PCR(-) were discharged from the NICU when clinically stable. The number of hours saved was calculated as (aLOS-eLOS). RESULTS: Approximately eight antibiotic doses and 85 NICU hours per infant could be saved using PCR(-) results available at 18 h. CONCLUSIONS: Use of 16S rRNA PCR could decrease the number of antibiotics doses and NICU LOS for infants admitted for EOS. This may facilitate: (1) earlier NICU discharge; (2) parental satisfaction; and (3) decreased health care costs.

Non-invasive measurement of reduced ventilation:perfusion ratio and shunt in infants with bronchopulmonary dysplasia: a physiological definition of the disease.

BACKGROUND: An objective definition of bronchopulmonary dysplasia (BPD) is required to interpret trial outcomes and provide a baseline for prognostic studies. Current definitions do not quantify disease severity. The cardinal measures of impaired gas exchange are a reduced ventilation:perfusion ratio (V(A):Q) and increased right to left shunt. These can be determined non-invasively by plotting arterial oxygen saturation (Spo(2)) against inspired oxygen pressure (PIo(2)). AIMS: To describe the reduced V(A):Q and shunt in infants with BPD and evaluate these as graded measures of pulmonary dysfunction. METHODS: 21 preterm infants with BPD were studied. PIo(2) was changed stepwise to vary Spo(2) between 86% and 94%. Pairs of PIo(2) and Spo(2) data points for each infant were plotted and analysed to derive reduced V(A):Q ratio and shunt. RESULTS: In every infant, the Spo(2) versus PIo(2) curve was shifted to the right of the normal because of a reduced V(A):Q. The mean (SD) shift was 16.5 (4.7) kPa (normal 6 kPa). Varying degrees of shunt were also present, but these were less important in determining Spo(2) within the studied range. The degree of shift was strongly predictive of the PIo(2) required to achieve any Spo(2) within the range 86-94% (R(2)>0.9), permitting shift and V(A):Q to be determined from a single pair of PIo(2) and SpO(2) values in this range. CONCLUSIONS: The predominant gas exchange impairment in BPD is a reduced V(A):Q, described by the right shift of the Spo(2) versus PIo(2) relationship. This provides a simpler method for defining BPD, which can grade disease severity.

The 'fixed performance' venturi: effect of downstream pressure on outflow and FIO2.

Fixed performance venturi devices should provide a predetermined oxygen concentration at an outflow which exceeds an adult's peak resting inspiratory flow rate (approximately 30 l.min(-1)). Campbell's original description mentioned the sensitivity of the venturi device to downstream resistance but gave no further details. This study examined outflow and oxygen concentration from the five standard venturi devices (24-60% O(2)) when downstream pressure increased. Outflow was exquisitely sensitive to small increases in pressure. The outflow at zero downstream pressure for the 24-40% O(2) venturi devices ranged from 40 to 50 l.min(-1) but only 2-3 mmH(2)O was needed to halve this flow and increase oxygen concentration. The 60% O(2) venturi delivered a maximum of only 30 l.min(-1) at zero downstream pressure and flow was reduced further by increasing this pressure. An increase in downstream pressure of only a few mmH(2)O increased oxygen concentration and decreased outflow of all the venturi devices tested, in most to less than normal peak tidal flow in adults.